1. Technical Field of the Invention
The present invention relates to an image reader suitable for a color copying apparatus.
2. Description of the Prior Art
As originals for a color copying apparatus, there may be mixed color originals and monochrome originals. With respect to monochrome originals, higher-quality output results can be obtained by performing image processing specific to the monochrome originals rather than that for the color originals. Also, in a popular type color copying apparatus, the output time can be shortened when it is set to a monochrome mode in advance because a common printer engine is sequentially used for each of YMCK colors.
Since it is troublesome for the user to set a mode of operation for each original, the color copying apparatus side generally distinguishes color from monochrome of the original to set the mode of operation in accordance with the distinction result. Also, in the color copying apparatus, in a case where the entire original is lightly discolored yellow, a so-called base color removal process for converting the information into xe2x80x9cwhitexe2x80x9d is preferably performed. In the case of performing this process, the base color level must also be detected in advance.
In order to perform such color/monochrome distinction and base color level detection as described above, prescan (before the original image reading, rough scan to be performed in advance at a speed several times faster than it) has been generally performed in the conventional color copying apparatus. Since the color/monochrome distinction of the original and the detection of the base color level can be performed by performing the prescan once, the image output can be started substantially the moment reading of the original image is finished on scanning (hereinafter, referred to as image scan) for the originally-designed image reading.
In this respect, as a monochrome-only copying apparatus, there has been known a copying apparatus capable of starting the image output at a point of time whereat the original image has been read to some degree without performing the prescan (for example, Japanese Published Unexamined Patent Application No. 8-191370). In the color copying apparatus, however, it is difficult to distinguish color from monochrome of the original and to determine the base color level when the original image has been read up to a certain part. This is because there may be cases where even if portions which have already been read are all monochrome, a color pattern exists in the remaining portion, and where the base color level must be changed when the yellow-discolored state of the original differs depending upon the place, among the others.
As described above, there is the problem that when the prescan is performed in the color copying apparatus, the productivity is deteriorated by time corresponding to the prescan. The present invention has been achieved in the light of the above-described state of affairs, and provides an image reader capable of performing image output at high speed.
The image reader has an image reading unit that reads an image of an original as image data to be expressed in a first color space, an image accumulation unit that accumulates the image data read by the image reading unit, an attribute distinction unit that distinguishes an attribute of the image data read by the image reading unit, a setting unit that sets a conversion characteristic of the image data in response to the attribute distinguished by the attribute distinction unit, and a conversion unit that converts the image data accumulated in the image accumulation unit into image data to be expressed in a second color space in accordance with the conversion characteristic set by the setting unit.
In the image reader, the attribute of the input image data may contain at least one of a size of the original, a base color level of the input image data, and whether the input image data is monochromatic or colored. The image reader may further include a path bypassing the image accumulation unit to supply the input image data to the attribute distinction unit.
In the image reader, the image reading unit may sequentially read images of multiple originals to output them as the input image data, and the image accumulation unit may have multiple memory banks, each having a capacity for storing input image data of one original. The image accumulation unit may write new input image data in one of the memory banks and at the same time, the unit may output input image data already written from another memory bank.
In the image reader, the image reading unit may sequentially read contents of multiple originals to output them as the input image data, and the image accumulation unit may write new input image data and at the same time, the unit may output the input image data already written.
In the image reader, the attribute may be distinguished in the attribute distinction unit in parallel with accumulation of the input image data in the image accumulation unit.
The present invention also provides an image reader for reading an original set on an automatic document feeder or a platen glass, having a determination unit that determines whether the original has been set on the automatic document feeder or the platen glass, and an image input unit that performs, if the determination unit determines that the original has been set on the platen glass, an image scan after an attribute of image data of the original is distinguished using a prescan, and that performs, if the determination unit determines that the original has been set on the automatic document feeder, the image scan without performing the prescan.
The present invention also provides an image reader for reading an original set on an automatic document feeder or a platen glass, having a determination unit that determines whether the original has been set on the automatic document feeder, and whether a number of copies is not more than a predetermined number, and an image input unit that performs an image scan after an attribute of image data of the original is distinguished using a prescan if a result of the determination by the determination unit is negative, and performs the image scan without performing the prescan if the result of determination is affirmative.
The present invention also provides an image reader for reading an original, having an operating unit that sets a magnification ratio for reproducing the original, and an image input unit that performs an image scan without performing a prescan if the magnification ratio of 100% or its integral multiple has been set in the operating unit, and that performs the image scan after an attribute of image data of the original is distinguished using the prescan if the magnification ratio other than 100% or its integral multiple has been set.